This invention relates to a bobbin and cover assembly and, more particularly, to a molded insulating bobbin and cover assembly for use in the manufacture of an electrical solenoid.
Electrical coil assemblies, such as used in transformers, relays, solenoids and indicators, have heretofore been conventionally made by winding a continuous length of insulated magnet wire onto a core piece of a spool or bobbin. The coating on the wire provided insulation between the adjacent turns of the wire. It was found that the insulation was often damaged during manufacture of the electrical coil assembly and that additional insulation was needed for many applications to prevent short circuiting between turns of the wire and between the leads. Thus, it was found expedient to impregnate the formed coil with varnish and then bake the same. For some uses, the varnishing and baking procedures were repeated a second time. Afterwards, insulating tape was affixed about the coil to minimize mechanical damage. This electrical coil assembly manufacturing procedure was obviously slow and relatively expensive.
The electrical coil assemblies are commonly provided with a plurality of conductive terminal lugs on the bobbin, such lugs being secured to the ends of the wire forming the coil. A problem found in such constructions is that the connections of the wire to the lugs cannot inherently be insulated from one another or from other components in the circuit or in the electrical assembly adjacent to the coil without the use of added secondary insulating tapes or the like.
Heretofore, the electrical coil assembly was generally positioned on the support therefor without provision of means to prevent the electrical coil from rotating with respect to the support and for spacing the electrical coil from the support.
U.S Pat. No. 3,230,490 disclosed structure which resolved many of the prior difficulties described. The coil assembly of U.S. Pat. No. 3,230,490 did not, however, lend itself to totally satisfactory utilization as a component for the manufacture of solenoids. For example, the core piece of a solenoid rides in the center tubular member of the disclosed coil assembly. Because of tolerance problems, the core piece tended to bind or alternatively vibrate loosely. To overcome this and additional problems, the improved solenoid coil of the present invention was devised.